Chronic obstructive pulmonary disease (COPD) is responsible for more than 500,000 hospitalizations and over 100,000 deaths in the United States annually. COPD is currently the fourth leading cause of death;it is projected to become the third leading cause of death in the U.S. by 2020 and worldwide by 2030. Long-term oxygen therapy (LTOT), which is administered to patients via a nasal cannula attached to an oxygen source, such as an oxygen concentrator or compressed-gas or liquid oxygen cylinder is the only treatment that has been shown to improve survival in severe hypoxemia due to cardiopulmonary diseases;the improvement in mortality is greatest when oxygen is prescribed 24/7. LTOT is also associated with significant reductions in hospitalizations and lengths of stay, and improved quality of life. The benefits of adherence to LTOT are substantial both to COPD patients (in terms of morbidity and mortality) and to society (in terms of healthcare cost savings). Clinicians and researchers currently assess adherence to LTOT over a given period by calculating the average daily use as determined via one of the following methods: (1) recording the hour-meter readings of oxygen con- centrators;(2) counting usage of oxygen cylinders;or (3) weighing liquid oxygen reservoirs. The concentrator's hour-meter reading provides only equipment \power-on" time over a given period. The number of cylinders used, or the change in weight of cylinder liquid oxygen reservoirs, reveals only the amount of oxygen expended. All of these measures of patient adherence fail to discern if the patient is actually wearing the nasal cannula or inhaling oxygen, as opposed to merely having the oxygen source turned on. Furthermore, current measures fail to provide information regarding the pattern of oxygen use within each 24-hour interval. There is currently no reliable means available in clinical practice or in research settings for assessing LTOT adherence. Nor is there a reliable means to monitor oxygen adherence for cost containment. Studies based on available methods for assessing adherence to LTOT indicate that many patients do not follow their physician's prescribed treatment regimen, resulting in inadequate therapy and wasted reimbursement dollars. For physicians to be able to communicate with their patients on a regular basis regarding their LTOT treatment and the importance of adherence to their health, it is essential to have accurate and objective measures of patients'adherence. The proposed Phase I project will establish a Continuous Oxygen Monitor for Patients on Long-term oxygen therapy (COMPLY) functional prototype that objectively determines the duration and pattern of adherence with oxygen therapy on a minute-by-minute basis. With the development and demonstration in Phase I of a reliable monitor that can measure patient adherence 24/7, the Phase II effort will focus on developing a commercial product prototype that also oers Internet-linked monitoring by healthcare providers and an interactive patient interface that provides informational, intentional, educational, and motivational feedback to encourage and improve adherence and, correspondingly, health outcomes. PUBLIC HEALTH RELEVANCE: The patient community receiving LTOT numbers approximately 800,000, and the cost of their oxygen therapy alone represents approximately 30% ($1.3 billion) of total Medicare expenditures for durable medical equipment. An objective and accurate method of measuring patient adherence to LTOT is required to augment clinical electiveness and cost containment for the long term, and for research studies to address such controversies as the benefits of LTOT in patients with intermittent hypoxemia. The proposed system will provide an elective, practical, and fordable method for reliably assessing LTOT adherence in clinical practice and research settings.